Lighting devices and methods for use

ABSTRACT

An example device is configured to emit a first light having a first luminous flux and a peak intensity at a first wavelength that is greater than or equal to 400 nanometers (nm) and less than or equal to 480 nm. The first luminous flux is variable and/or the emission of the first light is interrupted one or more times. The device is also configured to emit a second light having a second luminous flux and a peak intensity at a second wavelength that is greater than or equal to 500 nm and less than or equal to 630 nm. The second luminous flux is variable and/or the emission of the second light is interrupted one or more times. The first luminous flux is at a maximum at least during a time at which the second luminous flux is not at a maximum.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 62/508,286, filed on May 18, 2017, claims the benefit ofU.S. Provisional Patent Application No. 62/546,475, filed on Aug. 16,2017, and claims the benefit of International (PCT) Application No.PCT/US2018/020395, filed on Mar. 1, 2018, the contents of all of whichare incorporated herein by reference in their entirety.

BACKGROUND

Unless otherwise indicated herein, the materials described in thissection are not prior art to the claims in this application and are notadmitted to be prior art by inclusion in this section.

It may be useful to alter a person's circadian rhythm or “sleep cycle”for reasons such as jet lag and adjustment to non-traditional workshifts. A person's circadian rhythm is principally governed by thesuprachiasmatic nucleus (SCN), which is a small region within thebrain's hypothalamus. Previous methods for altering a person's circadianrhythm have generally involved direct stimulation of the light-sensitiveprotein melanopsin within intrinsically photosensitive retinal ganglioncells (ipRGCs) that make up about 1% of retinal ganglion cells withinthe retina. It is thought that illumination of the retina with bluelight (e.g, peak wavelength of about 480 nanometers) causes melanopsinexcited within a person's ipRGCs to stimulate the SCN via neuralpathways, thereby altering the person's circadian rhythm (e.g., delayingthe onset of tiredness). However, due to the ipRGCs' relatively lowphotosensitivity, their relatively sparse presence within the retina,and slow photoactive response, such methods may undesirably involveilluminating the retina with intensities that are unpleasant or evenpainful, for relatively long periods of time.

SUMMARY

One example describes a device that includes a light source assembly anda control system configured to cause the light source assembly toperform functions. The functions include emitting a first light having afirst luminous flux and a peak intensity at a first wavelength that isgreater than or equal to 400 nanometers (nm) and less than or equal to480 nm. The first luminous flux is variable or the emission of the firstlight is interrupted one or more times. The functions further includeemitting a second light having a second luminous flux and a peakintensity at a second wavelength that is greater than or equal to 500 nmand less than or equal to 630 nm. The second luminous flux is variableor the emission of the second light is interrupted one or more times.The first luminous flux is at a maximum at least during a time at whichthe second luminous flux is not at a maximum.

Another example describes a method that includes emitting, via a lightsource assembly, a first light having a first luminous flux and a peakintensity at a first wavelength that is greater than or equal to 400nanometers (nm) and less than or equal to 480 nm. The first luminousflux is variable or the emission of the first light is interrupted oneor more times. The method further includes emitting, via the lightsource assembly, a second light having a second luminous flux and a peakintensity at a second wavelength that is greater than or equal to 500 nmand less than or equal to 630 nm. The second luminous flux is variableor the emission of the second light is interrupted one or more times.The first luminous flux is at a maximum at least during a time at whichthe second luminous flux is not at a maximum.

Yet another example describes a white light source having a colorrendering index of greater than 70 as compared to daylight, a blackbody,or another lighting reference standard. The white light source isconfigured to emit light with a peak wavelength within a range of 480 nmto 580 nm.

Yet another example describes a light source that includes one or morediscrete light emitting diodes (LEDs) configured to emit first lighthaving a peak intensity within a range of 480 nm to 560 nm. The lightsource further includes one or more white LEDs having a color renderingindex higher than 70 when compared to daylight, a blackbody, or anotherlighting reference standard, the one or more white LEDs being configuredto emit second light such that the first light and the second lightcombined have a peak intensity at a wavelength within a range of 480 nmto 580 nm.

Yet another example describes a device that includes a light sourceassembly and a control system configured to cause the light sourceassembly to emit light having a luminous flux and a peak intensity at awavelength that is greater than or equal to 400 nanometers (nm) and lessthan or equal to 480 nm. The luminous flux is variable or the emissionof the light is interrupted one or more times.

Yet another example describes one or more light sources configured toemit: a first light having a peak wavelength within a range of 470 nm to580 nm and a second white light having a color rendering index ofgreater than 70 when compared to daylight, a blackbody, or anotherlighting reference standard. A luminous flux of the second light is lessthan a luminous flux of the first light.

Yet another example describes one or more light sources configured toemit: a first light having a peak wavelength within a range of 600 nm to700 nm and a second white light having a color rendering index ofgreater than 70 when compared to daylight, a blackbody, or anotherlighting reference standard. A luminous flux of the second light is lessthan a luminous flux of the first light.

Yet another example describes a device that includes one or more lightsources configured to emit first light having a color rendering index ofgreater than 70 when compared to daylight, a blackbody, or anotherlighting reference standard, and one or more phosphors that, whenilluminated by the one or more light sources, emit second light suchthat the first light and the second light combined have a peak intensityat a wavelength within a range of 470 nm to 580 nm.

Yet another example describes a device that includes a light sourceassembly and a control system configured to cause the light sourceassembly to perform functions. The functions include emitting a firstlight having a first luminous flux and a peak intensity at a firstwavelength that is greater than or equal to 400 nanometers (nm) and lessthan or equal to 440 nm. The first luminous flux is variable or theemission of the first light is interrupted one or more times. Thefunctions further include emitting a second light having a secondluminous flux and having a color correlated temperature of greater thanor equal to 2500 Kelvin and less than or equal to 6000 Kelvin. Thesecond luminous flux is variable or the emission of the second light isinterrupted one or more times and the second light has a color renderingindex greater than 70 when compared to daylight, a blackbody, or anotherlighting reference standard. The first luminous flux is at a maximum atleast during a time at which the second luminous flux is not at amaximum.

Yet another example describes a method that includes emitting, via alight source assembly, a first light having a first luminous flux and apeak intensity at a first wavelength that is greater than or equal to400 nanometers (nm) and less than or equal to 440 nm. The first luminousflux is variable or the emission of the first light is interrupted oneor more times. The method further includes emitting, via the lightsource assembly, a second light having a second luminous flux and havinga color correlated temperature of greater than or equal to 2500 Kelvinand less than or equal to 6000 Kelvin. The second luminous flux isvariable or the emission of the second light is interrupted one or moretimes. The second light has a color rendering index greater than 70 whencompared to daylight, a blackbody, or another lighting referencestandard. The first luminous flux is at a maximum at least during a timeat which the second luminous flux is not at a maximum.

Yet another example describes a plurality of light sources configured toemit light having a peak wavelength within a range of 400 nm to 440 nm.

Yet another example describes a white light source having a colorrendering index of greater than 70 as compared to daylight, a blackbody,or another lighting reference standard. The white light source isconfigured to emit light with a peak wavelength within a range of 400 nmto 440 nm.

Yet another example describes a device that includes a light sourceassembly; and a control system configured to cause the light sourceassembly to perform functions comprising: emitting a first light havinga first luminous flux and a peak intensity at a first wavelength that isgreater than or equal to 680 nanometers (nm) and less than or equal to750 nm, wherein the first luminous flux is variable or the emission ofthe first light is interrupted one or more times; and emitting a secondlight having a second luminous flux and a peak intensity at a secondwavelength that is less than or equal to 680 nm, wherein the secondluminous flux is variable or the emission of the second light isinterrupted one or more times, wherein the first luminous flux is at amaximum at least during a time at which the second luminous flux is notat a maximum.

Yet another example describes a method that includes emitting, via alight source assembly, a first light having a first luminous flux and apeak intensity at a first wavelength that is greater than or equal to680 nanometers (nm) and less than or equal to 750 nm, wherein the firstluminous flux is variable or the emission of the first light isinterrupted one or more times; and emitting, via the light sourceassembly, a second light having a second luminous flux and a peakintensity at a second wavelength that is less than or equal to 680 nm,wherein the second luminous flux is variable or the emission of thesecond light is interrupted one or more times, wherein the firstluminous flux is at a maximum at least during a time at which the secondluminous flux is not at a maximum.

Yet another example describes a device that includes a light sourceassembly; and a control system configured to cause the light sourceassembly to perform functions comprising: emitting a first light havinga first luminous flux and a peak intensity at a first wavelength that isgreater than or equal to 400 nanometers (nm) and less than or equal to440 nm, wherein the first luminous flux is variable or the emission ofthe first light is interrupted one or more times; and emitting a secondlight having a second luminous flux and a peak intensity at a secondwavelength that is greater than or equal to 440 nm, wherein the secondluminous flux is variable or the emission of the second light isinterrupted one or more times, wherein the first luminous flux is at amaximum at least during a time at which the second luminous flux is notat a maximum.

Yet another example describes a method that includes emitting, via alight source assembly, a first light having a first luminous flux and apeak intensity at a first wavelength that is greater than or equal to400 nanometers (nm) and less than or equal to 440 nm, wherein the firstluminous flux is variable or the emission of the first light isinterrupted one or more times; and emitting, via the light sourceassembly, a second light having a second luminous flux and a peakintensity at a second wavelength that is greater than or equal to 440nm, wherein the second luminous flux is variable or the emission of thesecond light is interrupted one or more times, wherein the firstluminous flux is at a maximum at least during a time at which the secondluminous flux is not at a maximum.

Yet another example includes a light source that includes one or morefirst light emitting diodes (LEDs) configured to emit first light havinga peak intensity within a range of 400 nm to 440 nm; and one or moresecond LEDs configured to emit second light having a peak intensitygreater than 440 nm, the first light and the second light combinedhaving a peak intensity at a wavelength within a range of 400 nm to 440nm.

Yet another example describes a method comprising: emitting, via one ormore first light emitting diodes (LEDs) of a light source, first lighthaving a peak intensity within a range of 400 nm to 440 nm; andemitting, via one or more second LEDs of the light source, second lighthaving a peak intensity greater than 440 nm, the first light and thesecond light combined having a peak intensity at a wavelength within arange of 400 nm to 440 nm.

These, as well as other aspects, advantages, and alternatives willbecome apparent to those of ordinary skill in the art by reading thefollowing detailed description, with reference where appropriate to theaccompanying drawings. Further, it should be understood that thissummary and other descriptions and figures provided herein are intendedto illustrate the invention by way of example only and, as such, thatnumerous variations are possible.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a lighting device, according to anexample embodiment.

FIG. 2 is a block diagram of a method, according to an exampleembodiment.

FIG. 3 illustrates intrinsically photosensitive retinal ganglion cell(ipRGC) response to excitation of S-type cones.

FIG. 4 illustrates ipRGC response to excitation of L-type and/or M-typecones.

FIG. 5 illustrates ipRGC response to excitation of various types ofupstream ganglion cells.

FIG. 6 includes photosensitivity curves of four types of ganglion cellsin the eye.

FIG. 7 illustrates the manipulation of circadian rhythm via retinaillumination at varying times of day.

FIG. 8 illustrates an advancement of circadian rhythm.

FIG. 9 illustrates a delay of circadian rhythm.

FIG. 10 illustrates an example intensity curve for a light source.

FIG. 11 illustrates example intensity curves for various types of lightsources.

FIG. 12 is a block diagram of a method, according to an exampleembodiment.

FIG. 13 is a block diagram of a method, according to an exampleembodiment.

FIG. 14 is a block diagram of a method, according to an exampleembodiment.

FIG. 15 is a block diagram of a method, according to an exampleembodiment.

DETAILED DESCRIPTION

As discussed above, current methods for altering circadian rhythm viadirect stimulation of melanopsin within intrinsically photosensitiveretinal ganglion cells (ipRGCs) are often inconvenient, unpleasant,and/or somewhat ineffective. Accordingly, improved devices and methodsfor altering circadian rhythm are disclosed herein.

The present inventors have appreciated that circadian rhythm can bealtered more conveniently and efficiently via stimulation of S-cones,M-cones, and L-cones within the eye, which causes indirect stimulationof ipRGCs that are downstream of the cones along neural pathways.Whereas previous methods involve illuminating ipRGCs with blue light(e.g., λ˜480 nm) to optimize melanopsin photoactivity, the methodsdisclosed herein generally involve illuminating a retina withwavelengths optimized to stimulate S-cones having a maximumphotosensitivity at about 420-440 nm, M-cones having a maximumphotosensitivity at about 534-545 nm, and/or L-cones having a maximumphotosensitivity at about 564-580 nm.

More specifically, the inventors have appreciated that stimulation ofcones, which have a dense presence within the retina and higherphotosensitivity when compared to ipRGCs, can cause more intenseexcitation of ipRGCs than direct stimulation of the ipRGCs themselves.This increased excitation of the ipRGCs causes increased stimulation ofthe suprachiasmatic nucleus (SCN), causing larger changes in circadianrhythm.

In particular, the inventors have appreciated that ipRGCs are mostresponsive to sharp increases and decreases in illuminance of the cones.For example, the activity of ipRGCs (and the resultant activity of thedownstream SCN) is maximized in response to sharp increases inphotoabsorption by M-cones (e.g., green light) and L-cones (e.g., redlight), and sharp decreases in photoabsorption by S-cones (e.g., violetlight).

FIG. 1 depicts a (lighting) device 100 that includes a light sourceassembly 102 and a control system 104. In some examples, the lightsource assembly 102 may include one or more light sources such as lightemitting diodes (LEDs), incandescent bulbs, or halogen bulbs, but otherexamples are possible.

The control system 104 may take the form of any combination of softwareand/or hardware that is configured to cause the light source assembly102 and/or the device 100 to perform any of the functions that aredescribed herein. For example, the control system 104 may include one ormore Boolean circuits, programmable logic controllers (PLCs), and/orspecial purpose circuits configured to provide electrical power and/orcontrol signals to the light source assembly 102 for performing any ofthe functions described herein. Additionally, the control system 104 mayinclude one or more processors and a computer readable medium storinginstructions that, when executed by the processors, cause the lightsource assembly 102 and/or the device 100 to perform any of thefunctions described herein. The control system 104 may additionallyinclude a signal generator.

In various examples, the device 100 may be incorporated into or take theform of a wearable device, goggles, a headband, armwear, wristwear, or atherapeutic wearable device configured to shine light onto a subject'sretina. In some examples, the device 100 is incorporated into a vehiclesuch as an automobile, an airplane, a helicopter, a boat, a ship, or atrain. The device 100 could also be incorporated into a dashboard, anaccent lighting unit, a cabin general lighting unit, or a headlightunit. In various examples, the device 100 is incorporated into a displayunit such as a cell phone, a tablet computer, a monitor, or atelevision. The device 100 could also be incorporated into a lightingunit such as a lamp, a nightlight, a chandelier, or an overhead lightingunit.

In some embodiments, the device 100 may take the form of a white lightsource having a color rendering index of greater than 70 as compared todaylight, a blackbody, or another lighting reference standard, with thewhite light source being configured to emit light with a peak wavelengthwithin a range of 480 nm to 580 nm, or more specifically, within a rangeof 520 nm to 570 nm.

In some embodiments, the device 100 takes the form of a light sourcethat includes one or more discrete light emitting diodes (LEDs)configured to emit first light having a peak intensity within a range of480 nm to 560 nm, and one or more white LEDs having a color renderingindex higher than 70 when compared to daylight, a blackbody, or anotherlighting reference standard, the one or more white LEDs being configuredto emit second light such that the first light and the second lightcombined have a peak intensity at a wavelength within a range of 480 nmto 580 nm. In this context, the device 100 could be operated in thepresence of ambient light having one or more wavelengths within a rangeof 400 nm to 780 nm. In this context, at least 50%, at least 60%, atleast 70%, at least 80%, at least 90% or at least 95% of a powerspectral density of the first light might correspond to wavelengthswithin a range of 480 nm to 560 nm.

The term “white light” as used herein may refer to any polychromaticlight having a color rendering index greater than 70 as defined by theInternational Commission on Illumination (CIE) R_(a) scale. Such whitelight may include non-zero intensities throughout the visible spectrumof 400-700 nm. As such, a “white light source” may include any lightsource configured to generate white light as described above. The term“color rendering index” (CRI) as used herein may also be generallydefined with reference to the CIE R_(a) scale.

In some embodiments, the control system 104 is configured to cause thelight source assembly 102 to emit light having a luminous flux and apeak intensity at a wavelength that is greater than or equal to 400nanometers (nm) and less than or equal to 480 nm, the luminous fluxbeing variable or the emission of the light being interrupted one ormore times. More specifically, the peak intensity may occur within anyof the following wavelength ranges: 410-430 nm, 415-425 nm, 418-422 nm(as measured by a spectrophotometer having a tolerance of +/−2 nm). Suchluminous flux may take the form of a square wave, a sinusoidal wave, asawtooth wave, or a triangle wave. The luminous flux may be periodicwith a frequency that is less than or equal to 100 Hz, or less than orequal to 50 Hz. In this context, at least 50%, at least 60%, at least70%, at least 80%, at least 90% or at least 95% of a power spectraldensity of the light might correspond to wavelengths within a range of400 nm to 480 nm. Additionally, the luminous flux might periodicallyreach a minimum that is greater than zero or equal to zero.

The device 100 may be configured to illuminate a retina of a user withan illuminance that is less than or equal to 10,000 lux, less than orequal to 5,000 lux, less than or equal to 1,000 lux, less than or equalto 500 lux, less than or equal to 100 lux, less than or equal to 50 lux,less than or equal to 10 lux, or less than or equal to 1 lux. In thiscontext, illuminance is defined as Ev=ΦV/(4□π□r2), with ‘r’ being thedistance from the light source to the retina and ΦV being the luminousflux of the light source.

In another example, the device 100 may take the form of one or morelight sources configured to emit: a first light having a peak wavelengthwithin a range of 470 nm to 580 nm; and a second white light having acolor rendering index of greater than 70 when compared to daylight, ablackbody, or another lighting reference standard, the luminous flux ofthe second light being less than a luminous flux of the first light. Inthis context, at least 50%, at least 60%, at least 70%, at least 80%, atleast 90% or at least 95% of a power spectral density of the first lightmight correspond to wavelengths within a range of 470 nm to 580 nm.

In another example, the device 100 may take the form one or more lightsources configured to emit: a first light having a peak wavelengthwithin a range of 600 nm to 700 nm; and a second white light having acolor rendering index of greater than 70 when compared to daylight, ablackbody, or another lighting reference standard, the luminous flux ofthe second light being less than a luminous flux of the first light. Inthis context, at least 50%, at least 60%, at least 70%, at least 80%, atleast 90% or at least 95% of a power spectral density of the first lightmight correspond to wavelengths within a range of 600 nm to 700 nm.

In another example, the device 100 may take the form of one or morelight sources configured to emit first light having a color renderingindex of greater than 70 when compared to daylight, a blackbody, oranother lighting reference standard; and one or more phosphors that,when illuminated by the one or more light sources, emit second lightsuch that the first light and the second light combined have a peakintensity at a wavelength within a range of 470 nm to 580 nm. In thiscontext, at least 50%, at least 60%, at least 70%, at least 80%, atleast 90% or at least 95% of a power spectral density of the secondlight might correspond to wavelengths within a range of 470 nm to 580nm.

FIG. 2 is a block diagram of a method 200. The method 200 and relatedmethods disclosed herein can be performed to cause advancement or delayof a subject's circadian cycle for various purposes. Such methods can beperformed to treat a subject afflicted with seasonal affective disorder(SAD) or another mood disorder, such as depression, bipolar disorder, ordysthymia. Disrupted or irregular sleep can also affect those sufferingwith cancer and/or heart disease, and these methods can be usedaccordingly to counteract such effects.

At block 202, the method includes emitting, via a light source assembly,a first light having a first luminous flux and a peak intensity at afirst wavelength that is greater than or equal to 400 nanometers (nm)and less than or equal to 480 nm. In other words, the first light may bemost intense (or have a local maximum) at a wavelength that is greaterthan or equal to 400 nm and less than or equal to 480 nm. Morespecifically, the first wavelength may be greater than or equal to 410nm and less than or equal to 430 nm, greater than or equal to 415 nm andless than or equal to 425 nm, or greater than or equal to 418 nm andless than or equal to 422 nm.

As the term is used throughout this disclosure, light defined as havinga “peak intensity” within a certain range of wavelengths is not meant toexclude the possibility that the light might have a global peakintensity outside of the recited range of wavelengths. That is, the term“peak intensity” can refer to a local peak intensity and, in addition orin the alternative, to a global peak intensity.

In this context, the first luminous flux is variable or the emission ofthe first light is interrupted one or more times. For example, the firstluminous flux may take the form of a square wave, a sinusoidal wave, asawtooth wave, a triangle wave, or any digital or analog wave. Otherexamples are possible.

The first light may be emitted by the light source assembly 102 suchthat the first light illuminates a retina of a user with an illuminancethat is less than or equal to 10,000 lux, less than or equal to 5,000lux, less than or equal to 1,000 lux, less than or equal to 500 lux,less than or equal to 100 lux, less than or equal to 50 lux, less thanor equal to 10 lux, or less than or equal to 1 lux.

In one example, the light source assembly 102 emits a first light havinga luminous flux 302 as shown in FIG. 3. The luminous flux 302 has a peakintensity at a wavelength that is greater than or equal to 400 nm andless than or equal to 480 nm. The luminous flux 302 takes the form of asquare wave that oscillates between a high level of luminous flux 304and a low level of luminous flux 306. The low level of luminous flux 306could be zero or near zero, but the low level of luminous flux 306 isgenerally less than the high level of luminous flux 304. The luminousflux 302 having a peak intensity at a wavelength between 400-480 nmprimarily excites S-cones within the retina, resulting in a response 308of downstream ipRGCs. As shown, the response 308 is most frequent andintense immediately after the luminous flux 302 switches from the highlevel 304 to the low level 306 at t=0, for example. However, theresponse 308 continues at reduced intensity and frequency while theluminous flux 302 continues to be at the low level 306. The S-conesbecome relatively inactive after the luminous flux 302 switches to thehigh level 304.

In short, high response intensity and high response frequencies fordownstream ipRGCs occur in response to relatively quick negative changes(decreases) in the luminous flux of the first light having a peakintensity between 400 and 480 nm. Although FIG. 3 shows the luminousflux 302 in the form of a square wave, waveforms such as a sinusoidalwave, a sawtooth wave, or a triangle wave can also exhibit relativelyquick negative changes in luminous flux with peak intensity between 400nm and 480, thereby efficiently exciting downstream ipRGCs.

In particular embodiments, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90% or at least 95% of a power spectral density ofthe first light corresponds to wavelengths within a range of 400 nm to420 nm.

In particular embodiments, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90% or at least 95% of a power spectral density ofthe first light corresponds to wavelengths within a range of 420 nm to440 nm.

In particular embodiments, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90% or at least 95% of a power spectral density ofthe first light corresponds to wavelengths within a range of 440 nm to460 nm.

In particular embodiments, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90% or at least 95% of a power spectral density ofthe first light corresponds to wavelengths within a range of 460 nm to480 nm.

In particular embodiments, the first luminous flux periodically reachesa minimum that is greater than zero.

In particular embodiments, the first luminous flux periodically reachesa minimum that is equal to zero. At block 204, the method includesemitting, via the light source assembly, a second light having a secondluminous flux and a peak intensity at a second wavelength that isgreater than or equal to 500 nm and less than or equal to 630 nm. Inother words, the second light may be most intense (or have a localmaximum) at a wavelength that is greater than or equal to 500 nm andless than or equal to 630 nm. More specifically, the second wavelengthmay be greater than or equal to 535 nm and less than or equal to 565 nm,greater than or equal to 545 nm and less than or equal to 555 nm, orgreater than or equal to 548 nm and less than or equal to 552 nm.

In this context, the second luminous flux is variable or the emission ofthe second light is interrupted one or more times. For example, thesecond luminous flux may take the form of a square wave, a sinusoidalwave, a sawtooth wave, a triangle wave, or any other digital or analogwave. Other examples are possible.

The second light may be emitted by the light source assembly 102 suchthat the second light illuminates a retina of a user with an illuminancethat is less than or equal to 10,000 lux, less than or equal to 5,000lux, less than or equal to 1,000 lux, less than or equal to 500 lux,less than or equal to 100 lux, less than or equal to 50 lux, less thanor equal to 10 lux, or less than or equal to 1 lux.

In one example, the light source assembly 102 emits a second lighthaving a luminous flux 402 as shown in FIG. 4. The luminous flux 402 hasa peak intensity at a wavelength that is greater than or equal to 500 nmand less than or equal to 630 nm. The luminous flux 402 takes the formof a square wave that oscillates between a high level of luminous flux404 and a low level of luminous flux 406. The low level of luminous flux406 could be zero or near zero, but the low level of luminous flux 406is generally less than the high level of luminous flux 404. The luminousflux 402 having a peak intensity at a wavelength between 500-630 nmprimarily excites L-cones and M-cones within the retina, resulting in aresponse 408 of downstream ipRGCs. As shown, the response 408 is mostfrequent and intense immediately after the luminous flux 402 switchesfrom the low level 406 to the high level 404 at t=0, for example.However, the response 408 continues at reduced intensity and frequencywhile the luminous flux 402 continues to be at the high level 404. TheL-cones and M-cones become relatively inactive after the luminous flux402 switches to the low level 406.

In short, high response intensity and high response frequencies fordownstream ipRGCs occur in response to relatively quick positive changes(increases) in the luminous flux of the second light having a peakintensity between 500 and 630 nm. Although FIG. 4 shows the luminousflux 402 in the form of a square wave, waveforms such as a sinusoidalwave, a sawtooth wave, or a triangle wave can also exhibit relativelyquick positive changes in luminous flux with peak intensity between 500nm and 630, thereby efficiently exciting downstream ipRGCs.

In accordance with the method 200, the light source assembly 102 mayinclude a first light source configured to emit the first light (e.g.,luminous flux 302) and a second light source configured to emit thesecond light (e.g., luminous flux 402).

In various examples, the first luminous flux (e.g., luminous flux 302)is out of phase with the second luminous flux (e.g., luminous flux 402)by 180 degrees. Although less desirable, the phase difference betweenthe first luminous flux and the second luminous flux could rangeanywhere from 0 to 180 degrees. In some embodiments, the first luminousflux will be at a maximum when the second luminous flux is at a minimum.In some embodiments, the first luminous flux will be at a minimum whenthe second luminous flux is at a maximum.

In various examples, the first luminous flux (e.g., luminous flux 302)and the second luminous flux (e.g., luminous flux 402) take the form ofrespective square waves with equal respective duty cycles or otherwaveforms having equal respective duty cycles. However, the firstluminous flux and the second luminous flux can also take the form ofrespective square waves with unequal respective duty cycles or otherwaveforms having unequal respective duty cycles.

In various examples, the first luminous flux and the second luminousflux are periodic with respective oscillation frequencies that are lessthan or equal to 100 Hz. The first luminous flux and the second luminousflux may also be periodic with respective oscillation frequencies thatare less than or equal to 50 Hz. The ipRGCs within the eye generallydon't respond in synchrony with light that oscillates at frequenciesgreater than about 100 Hz.

In particular embodiments, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90% or at least 95% of a power spectral density ofthe second light corresponds to wavelengths within a range of 500 nm to530 nm.

In particular embodiments, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90% or at least 95% of a power spectral density ofthe second light corresponds to wavelengths within a range of 530 nm to560 nm.

In particular embodiments, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90% or at least 95% of a power spectral density ofthe second light corresponds to wavelengths within a range of 560 nm to590 nm.

In particular embodiments, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90% or at least 95% of a power spectral density ofthe second light corresponds to wavelengths within a range of 590 nm to630 nm.

In particular embodiments, the second luminous flux periodically reachesa minimum that is greater than zero.

In particular embodiments, the second luminous flux periodically reachesa minimum that is equal to zero.

FIG. 5 illustrates ipRGC response to excitation of various types ofupstream ganglion cells. As shown, ipRGCs 512 are stimulated by onset ofblue light 502, red light 506, green light 508, and rod excitation 510.The ipRGCs 512 are stimulated by offset of violet light 504.

FIG. 6 includes photosensitivity curves of four types of ganglion cellsin the eye. The curve 602 represents S-cones, the curve 604 representsthe melanopsin response of ipRGCs, the curve 606 represents M-cones, andthe curve 608 represents L-cones.

FIG. 7 illustrates the manipulation of circadian rhythm via retinaillumination at varying times of day. The methods disclosed herein willhave different effects depending on the time of day and/or the point atwhich the subject is currently at in their circadian rhythm. For atraditional circadian rhythm, the disclosed methods generally advancecircadian rhythm when performed in the morning, and delay circadianrhythm when performed in the late afternoon or evening. As shown in FIG.8, an “advancement” of circadian rhythm generally means one will becomesleepy sooner. As shown in FIG. 9, “delay” of circadian rhythm generallymeans one will become sleepy later.

FIG. 10 illustrates an example intensity curve for a steady state“white” light source. As shown, the light source has a peak intensityaround 570 nm.

FIG. 11 illustrates example intensity curves for various types of lightsources. Curve 702 is a “warm” white light source, curve 704 is a“neutral” white light source, and curve 706 is a “cool” white lightsource. The curve 708, in contrast to the other curves, exhibits amaximum intensity around 550 nm. Similar light sources might have amaximum at a wavelength anywhere from 520-570 nm.

FIG. 12 is a block diagram of a method 1200. The method 1200 and relatedmethods disclosed herein can be performed to cause advancement or delayof a subject's circadian cycle for various purposes. Such methods can beperformed to treat a subject afflicted with seasonal affective disorder(SAD) or another mood disorder, such as depression, bipolar disorder, ordysthymia. Disrupted or irregular sleep can also affect those sufferingwith cancer and/or heart disease, and these methods can be usedaccordingly to counteract such effects. The method 1200 may be performedwith the device 100, for example.

At block 1202, the method 1200 includes emitting, via a light sourceassembly, a first light having a first luminous flux and a peakintensity at a first wavelength that is greater than or equal to 400nanometers (nm) and less than or equal to 440 nm. The first luminousflux is variable or the emission of the first light is interrupted oneor more times. For example, the light source assembly 102 may emit thefirst light in any manner described above with respect to block 202 orblock 204 of the method 200.

At block 1204, the method 1200 includes emitting, via the light sourceassembly, a second light having a second luminous flux and having acolor correlated temperature of greater than or equal to 2500 Kelvin andless than or equal to 6000 Kelvin. The second luminous flux is variableor the emission of the second light is interrupted one or more times.The second light has a color rendering index greater than 70 whencompared to daylight, a blackbody, or another lighting referencestandard. For example, the light source assembly 102 may emit the secondlight in any manner described above with respect to block 202 or block204 of the method 200.

In various examples, the first light and/or the second light has anintensity spectrum that includes a finite range of wavelengths.

In some examples, the light source assembly includes a first lightsource configured to emit the first light and a second light sourceconfigured to emit the second light.

In particular examples, the light source assembly includes one or morelight emitting diodes (LEDs).

In certain examples, the first luminous flux is out of phase with thesecond luminous flux by 180 degrees.

In some embodiments, the first luminous flux will be at a maximum whenthe second luminous flux is at a minimum. In some embodiments, the firstluminous flux will be at a minimum when the second luminous flux is at amaximum.

In some examples, the first luminous flux and/or the second luminousflux takes the form of a square wave, a sinusoidal wave, a sawtoothwave, or a triangle wave.

In certain examples, the first luminous flux and the second luminousflux take the form of respective square waves with equal or unequalrespective duty cycles or other waveforms having equal or unequalrespective duty cycles.

In particular examples, the first luminous flux and the second luminousflux are periodic with respective frequencies that are less than orequal to 100 Hz or are less than or equal to 50 Hz.

In certain examples, emitting the first light and/or the second lightincludes emitting the first light and/or the second light such that thefirst light and/or the second light respectively illuminates a retina ofa user with an illuminance that is less than or equal to 10,000 lux,less than or equal to 5,000 lux, less than or equal to 1,000 lux, lessthan or equal to 500 lux, less than or equal to 100 lux, less than orequal to 50 lux, less than or equal to 10 lux, or less than or equal to1 lux.

In particular embodiments, the first luminous flux periodically reachesa minimum that is greater than zero.

In particular embodiments, the first luminous flux periodically reachesa minimum that is equal to zero.

Additional examples include a plurality of light sources (e.g., lightemitting diodes) configured to emit light having a peak wavelengthwithin a range of 400 nm to 440 nm. In particular examples, theplurality of light sources are configured to emit respective ranges ofwavelengths of light that are different from each other (e.g.,overlapping but non-identical). Additionally, the plurality of lightsources may be configured to collectively emit white light having acolor rendering index of greater than 70 as compared to daylight, ablackbody, or another lighting reference standard.

Additional examples include a white light source having a colorrendering index of greater than 70 as compared to daylight, a blackbody,or another lighting reference standard. The white light source isconfigured to emit light with a peak wavelength within a range of 400 nmto 440 nm.

Any of the devices or light sources described herein may be incorporatedinto a wearable device, including but not limited to goggles, aheadband, armwear, wristwear, or a therapeutic wearable deviceconfigured to shine light onto a subject's retina.

Any of the devices or light sources described herein may be incorporatedinto a vehicle including but not limited to an automobile, an airplane,a helicopter, a boat, a ship, or a train.

Any of the devices or light sources described herein may be incorporatedinto a dashboard, an accent lighting unit, a cabin general lightingunit, or a headlight unit.

Any of the devices or light sources described herein may be incorporatedinto a display unit, including but not limited to a cell phone, a tabletcomputer, a monitor, or a television.

Any of the devices or light sources described herein may be incorporatedinto a lighting unit including but not limited to a lamp, a nightlight,a chandelier, or an overhead lighting unit.

FIG. 13 is a block diagram of a method 1300. The method 1300 and relatedmethods disclosed herein can be performed to cause advancement or delayof a subject's circadian cycle for various purposes. Such methods can beperformed to treat a subject afflicted with seasonal affective disorder(SAD) or another mood disorder, such as depression, bipolar disorder, ordysthymia. Disrupted or irregular sleep can also affect those sufferingwith cancer and/or heart disease, and these methods can be usedaccordingly to counteract such effects.

At block 1302, the method 1300 includes emitting, via a light sourceassembly, a first light having a first luminous flux and a peakintensity at a first wavelength that is greater than or equal to 680nanometers (nm) and less than or equal to 750 nm. In other words, thefirst light may be most intense (or have a local maximum) at awavelength that is greater than or equal to 680 nm and less than orequal to 750 nm. More specifically, the first wavelength may be greaterthan or equal to 680 nm and less than or equal to 695 nm, greater thanor equal to 695 nm and less than or equal to 720 nm, or greater than orequal to 720 nm and less than or equal to 750 nm.

In this context, the first luminous flux is variable or the emission ofthe first light is interrupted one or more times. For example, the firstluminous flux may take the form of a square wave, a sinusoidal wave, asawtooth wave, a triangle wave, or any other digital or analog wave.Other examples are possible.

The first light may be emitted by the light source assembly 102 suchthat the first light illuminates a retina of a user with an illuminancethat is less than or equal to 10,000 lux, less than or equal to 5,000lux, less than or equal to 1,000 lux, less than or equal to 500 lux,less than or equal to 100 lux, less than or equal to 50 lux, less thanor equal to 10 lux, or less than or equal to 1 lux.

In one example, the light source assembly 102 emits a first light havinga luminous flux 402 as shown in FIG. 4. The luminous flux 402 has a peakintensity at a wavelength that is greater than or equal to 680 nm andless than or equal to 750 nm. The luminous flux 402 takes the form of asquare wave that oscillates between a high level of luminous flux 404and a low level of luminous flux 406. The low level of luminous flux 406could be zero or near zero, but the low level of luminous flux 406 isgenerally less than the high level of luminous flux 404. The luminousflux 402 having a peak intensity at a wavelength between 680-750 nmprimarily excites L-cones within the retina, resulting in a response 408of downstream ipRGCs. As shown, the response 408 is most frequent andintense immediately after the luminous flux 402 switches from the lowlevel 406 to the high level 404 at t=0, for example. However, theresponse 408 continues at reduced intensity and frequency while theluminous flux 402 continues to be at the high level 404. The L-conesbecome relatively inactive after the luminous flux 402 switches to thelow level 406.

In short, high response intensity and high response frequencies fordownstream ipRGCs occur in response to relatively quick positive changes(increases) in the luminous flux of the first light having a peakintensity between 680 and 750 nm. Although FIG. 4 shows the luminousflux 402 in the form of a square wave, waveforms such as a sinusoidalwave, a sawtooth wave, or a triangle wave can also exhibit relativelyquick positive changes in luminous flux with peak intensity between 680nm and 750, thereby efficiently exciting downstream ipRGCs.

In particular embodiments, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90% or at least 95% of a power spectral density ofthe first light corresponds to wavelengths within a range of 680 nm to695 nm.

In particular embodiments, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90% or at least 95% of a power spectral density ofthe first light corresponds to wavelengths within a range of 695 nm to720 nm.

In particular embodiments, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90% or at least 95% of a power spectral density ofthe first light corresponds to wavelengths within a range of 720 nm to750 nm.

In particular embodiments, the first luminous flux periodically reachesa minimum that is greater than zero.

In particular embodiments, the first luminous flux periodically reachesa minimum that is equal to zero.

At block 1304, the method 1300 includes emitting, via the light sourceassembly, a second light having a second luminous flux and a peakintensity at a second wavelength that is less than or equal to 680 nm.In other words, the second light may be most intense (or have a localmaximum) at a wavelength that is greater than or equal to 440 nm andless than or equal to 680 nm. More specifically, the second wavelengthmay be greater than or equal to 440 nm and less than or equal to 520 nm,greater than or equal to 520 nm and less than or equal to 600 nm, orgreater than or equal to 600 nm and less than or equal to 680 nm.

In this context, the second luminous flux is variable or the emission ofthe second light is interrupted one or more times. For example, thesecond luminous flux may take the form of a square wave, a sinusoidalwave, a sawtooth wave, a triangle wave, or any other digital or analogwave. Other examples are possible.

The second light may be emitted by the light source assembly 102 suchthat the second light illuminates a retina of a user with an illuminancethat is less than or equal to 10,000 lux, less than or equal to 5,000lux, less than or equal to 1,000 lux, less than or equal to 500 lux,less than or equal to 100 lux, less than or equal to 50 lux, less thanor equal to 10 lux, or less than or equal to 1 lux.

In one example, the light source assembly 102 emits a second lighthaving a luminous flux 302 as shown in FIG. 3. The luminous flux 302 hasa peak intensity at a wavelength that is greater than or equal to 440 nmand less than or equal to 680 nm. The luminous flux 302 takes the formof a square wave that oscillates between a high level of luminous flux304 and a low level of luminous flux 306. The low level of luminous flux306 could be zero or near zero, but the low level of luminous flux 306is generally less than the high level of luminous flux 304. In thiscontext, one purpose of the second light is to provide a contrastbalance with respect to the first light. That is, the first light havinga peak wavelength between 680 and 750 nm can be used to advance or delaycircadian rhythm in a subject, while the second light balances againstthe first light such that the subject perceives little or no variationin light intensity. In some examples, the first light might penetrate asubject's eyelids while the subject is sleeping. By further example, thelight source assembly 102 might be operated in a setting that issubstantially void of ambient light (e.g., has less than 10 lux ofambient light).

In accordance with the method 1300, the light source assembly 102 mayinclude a first light source configured to emit the first light (e.g.,luminous flux 402) and a second light source configured to emit thesecond light (e.g., luminous flux 302).

In various examples, the first luminous flux (e.g., luminous flux 402)is out of phase with the second luminous flux (e.g., luminous flux 302)by 180 degrees. Although less desirable, the phase difference betweenthe first luminous flux and the second luminous flux could rangeanywhere from 0 to 180 degrees.

In some embodiments, the first luminous flux will be at a maximum whenthe second luminous flux is at a minimum. In some embodiments, the firstluminous flux will be at a minimum when the second luminous flux is at amaximum.

In various examples, the first luminous flux (e.g., luminous flux 402)and the second luminous flux (e.g., luminous flux 302) take the form ofrespective square waves with equal respective duty cycles or otherwaveforms having equal respective duty cycles. However, the firstluminous flux and the second luminous flux can also take the form ofrespective square waves with unequal respective duty cycles or otherwaveforms having unequal respective duty cycles.

In various examples, the first luminous flux and the second luminousflux are periodic with respective oscillation frequencies that are lessthan or equal to 100 Hz. The first luminous flux and the second luminousflux may also be periodic with respective oscillation frequencies thatare less than or equal to 50 Hz.

In particular embodiments, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90% or at least 95% of a power spectral density ofthe second light corresponds to wavelengths within a range of 440 nm to680 nm.

In particular embodiments, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90% or at least 95% of a power spectral density ofthe second light corresponds to wavelengths within a range of 440 nm to520 nm.

In particular embodiments, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90% or at least 95% of a power spectral density ofthe second light corresponds to wavelengths within a range of 520 nm to600 nm.

In particular embodiments, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90% or at least 95% of a power spectral density ofthe second light corresponds to wavelengths within a range of 600 nm to680 nm.

In particular embodiments, the second luminous flux periodically reachesa minimum that is greater than zero.

In particular embodiments, the second luminous flux periodically reachesa minimum that is equal to zero.

FIG. 14 is a block diagram of a method 1400. The method 1400 and relatedmethods disclosed herein can be performed to cause advancement or delayof a subject's circadian cycle for various purposes. Such methods can beperformed to treat a subject afflicted with seasonal affective disorder(SAD) or another mood disorder, such as depression, bipolar disorder, ordysthymia. Disrupted or irregular sleep can also affect those sufferingwith cancer and/or heart disease, and these methods can be usedaccordingly to counteract such effects.

At block 1402, the method 1400 includes emitting, via a light sourceassembly, a first light having a first luminous flux and a peakintensity at a first wavelength that is greater than or equal to 400nanometers (nm) and less than or equal to 440 nm. In other words, thefirst light may be most intense (or have a local maximum) at awavelength that is greater than or equal to 400 nm and less than orequal to 440 nm. More specifically, the first wavelength may be greaterthan or equal to 400 nm and less than or equal to 415 nm, greater thanor equal to 415 nm and less than or equal to 430 nm, or greater than orequal to 430 nm and less than or equal to 440 nm.

In this context, the first luminous flux is variable or the emission ofthe first light is interrupted one or more times. For example, the firstluminous flux may take the form of a square wave, a sinusoidal wave, asawtooth wave, a triangle wave, or any other digital or analog wave.Other examples are possible.

The first light may be emitted by the light source assembly 102 suchthat the first light illuminates a retina of a user with an illuminancethat is less than or equal to 10,000 lux, less than or equal to 5,000lux, less than or equal to 1,000 lux, less than or equal to 500 lux,less than or equal to 100 lux, less than or equal to 50 lux, less thanor equal to 10 lux, or less than or equal to 1 lux.

In one example, the light source assembly 102 emits a first light havinga luminous flux 302 as shown in FIG. 3. The luminous flux 302 has a peakintensity at a wavelength that is greater than or equal to 400 nm andless than or equal to 440 nm. The luminous flux 302 takes the form of asquare wave that oscillates between a high level of luminous flux 304and a low level of luminous flux 306. The low level of luminous flux 306could be zero or near zero, but the low level of luminous flux 306 isgenerally less than the high level of luminous flux 304. The luminousflux 302 having a peak intensity at a wavelength between 400-440 nmprimarily (e.g., upon turn off) excites S-cones within the retina,resulting in a response 308 of downstream ipRGCs. As shown, the response308 is most frequent and intense immediately after the luminous flux 302switches from the high level 304 to the low level 306 at t=0, forexample. However, the response 308 continues at reduced intensity andfrequency while the luminous flux 302 continues to be at the low level306. The S-cones become relatively inactive after the luminous flux 302switches to the high level 304.

In short, high response intensity and high response frequencies fordownstream ipRGCs occur in response to relatively quick negative changes(decreases) in the luminous flux of the first light having a peakintensity between 400 and 440 nm. Although FIG. 3 shows the luminousflux 302 in the form of a square wave, waveforms such as a sinusoidalwave, a sawtooth wave, or a triangle wave can also exhibit relativelyquick negative changes in luminous flux with peak intensity between 400nm and 440 nm, thereby efficiently exciting downstream ipRGCs.

In particular embodiments, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90% or at least 95% of a power spectral density ofthe first light corresponds to wavelengths within a range of 400 nm to415 nm.

In particular embodiments, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90% or at least 95% of a power spectral density ofthe first light corresponds to wavelengths within a range of 415 nm to430 nm.

In particular embodiments, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90% or at least 95% of a power spectral density ofthe first light corresponds to wavelengths within a range of 430 nm to440 nm.

In particular embodiments, the first luminous flux periodically reachesa minimum that is greater than zero.

In particular embodiments, the first luminous flux periodically reachesa minimum that is equal to zero.

At block 1404, the method 1400 includes emitting, via the light sourceassembly, a second light having a second luminous flux and a peakintensity at a second wavelength that is greater than or equal to 440 nmand less than or equal to 680 nm. In other words, the second light maybe most intense (or have a local maximum) at a wavelength that isgreater than or equal to 440 nm and less than or equal to 680 nm. Morespecifically, the second wavelength may be greater than or equal to 440nm and less than or equal to 520 nm, greater than or equal to 520 nm andless than or equal to 600 nm, or greater than or equal to 600 nm andless than or equal to 680 nm.

In this context, the second luminous flux is variable or the emission ofthe second light is interrupted one or more times. For example, thesecond luminous flux may take the form of a square wave, a sinusoidalwave, a sawtooth wave, a triangle wave, or any other digital or analogwave. Other examples are possible.

The second light may be emitted by the light source assembly 102 suchthat the second light illuminates a retina of a user with an illuminancethat is less than or equal to 10,000 lux, less than or equal to 5,000lux, less than or equal to 1,000 lux, less than or equal to 500 lux,less than or equal to 100 lux, less than or equal to 50 lux, less thanor equal to 10 lux, or less than or equal to 1 lux.

In one example, the light source assembly 102 emits a second lighthaving a luminous flux 402 as shown in FIG. 4. The luminous flux 402 hasa peak intensity at a wavelength that is greater than or equal to 440 nmand less than or equal to 680 nm. The luminous flux 402 takes the formof a square wave that oscillates between a high level of luminous flux404 and a low level of luminous flux 406. The low level of luminous flux406 could be zero or near zero, but the low level of luminous flux 406is generally less than the high level of luminous flux 404. In thiscontext, one purpose of the second light is to provide a contrastbalance with respect to the first light. That is, the first light havinga peak wavelength between 400 and 440 nm can be used (e.g., as part of awearable device) to advance or delay circadian rhythm in a subject,while the second light balances against the first light such that thesubject perceives little or no variation in light intensity.

In accordance with the method 1400, the light source assembly 102 mayinclude a first light source configured to emit the first light (e.g.,luminous flux 302) and a second light source configured to emit thesecond light (e.g., luminous flux 402).

In various examples, the first luminous flux (e.g., luminous flux 302)is out of phase with the second luminous flux (e.g., luminous flux 402)by 180 degrees. Although less desirable, the phase difference betweenthe first luminous flux and the second luminous flux could rangeanywhere from 0 to 180 degrees. In some embodiments, the first luminousflux will be at a maximum when the second luminous flux is at a minimum.In some embodiments, the first luminous flux will be at a minimum whenthe second luminous flux is at a maximum.

In various examples, the first luminous flux (e.g., luminous flux 302)and the second luminous flux (e.g., luminous flux 402) take the form ofrespective square waves with equal respective duty cycles or otherwaveforms having equal respective duty cycles. However, the firstluminous flux and the second luminous flux can also take the form ofrespective square waves with unequal respective duty cycles or otherwaveforms having unequal respective duty cycles.

In various examples, the first luminous flux and the second luminousflux are periodic with respective oscillation frequencies that are lessthan or equal to 100 Hz. The first luminous flux and the second luminousflux may also be periodic with respective oscillation frequencies thatare less than or equal to 50 Hz.

In particular embodiments, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90% or at least 95% of a power spectral density ofthe second light corresponds to wavelengths within a range of 440 nm to680 nm.

In particular embodiments, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90% or at least 95% of a power spectral density ofthe second light corresponds to wavelengths within a range of 440 nm to520 nm.

In particular embodiments, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90% or at least 95% of a power spectral density ofthe second light corresponds to wavelengths within a range of 520 nm to600 nm.

In particular embodiments, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90% or at least 95% of a power spectral density ofthe second light corresponds to wavelengths within a range of 600 nm to680 nm.

In particular embodiments, the second luminous flux periodically reachesa minimum that is greater than zero.

In particular embodiments, the second luminous flux periodically reachesa minimum that is equal to zero.

In particular embodiments, the second light has a color rendering indexof greater than 70 as compared to daylight, a blackbody, or anotherlighting reference standard.

FIG. 15 is a block diagram of a method 1500. The method 1500 and relatedmethods disclosed herein can be performed to help prevent changes (e.g.,time shifts) to a subject's circadian cycle for various purposes. Suchmethods can be performed to treat a subject afflicted with seasonalaffective disorder (SAD) or another mood disorder, such as depression,bipolar disorder, or dysthymia. Disrupted or irregular sleep can alsoaffect those suffering with cancer and/or heart disease, and thesemethods can be used accordingly to counteract such effects.

At block 1502, the method 1500 includes emitting, via one or more firstlight emitting diodes (LEDs) of a light source, first light having apeak intensity within a range of 400 nm to 440 nm. In other words, thefirst light may be most intense (or have a local maximum) at awavelength that is greater than or equal to 400 nm and less than orequal to 440 nm. More specifically, the first wavelength may be greaterthan or equal to 400 nm and less than or equal to 415 nm, greater thanor equal to 415 nm and less than or equal to 430 nm, or greater than orequal to 430 nm and less than or equal to 440 nm.

The one or more first LEDs that emit the first light may be part of thelight source 102, for example.

In particular embodiments, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90% or at least 95% of a power spectral density ofthe first light corresponds to wavelengths within a range of 400 nm to440 nm.

In particular embodiments, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90% or at least 95% of a power spectral density ofthe first light corresponds to wavelengths within a range of 400 nm to415 nm.

In particular embodiments, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90% or at least 95% of a power spectral density ofthe first light corresponds to wavelengths within a range of 415 nm to430 nm.

In particular embodiments, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90% or at least 95% of a power spectral density ofthe first light corresponds to wavelengths within a range of 430 nm to440 nm.

At block 1504, the method 1500 includes emitting, via one or more secondLEDs of the light source, second light having a peak intensity within arange of 400 nm to 440 nm. In this context, the first light and thesecond light combined have a peak intensity at a wavelength within arange of 400 nm to 440 nm.

In particular embodiments, the second light has a color rendering indexhigher than 70 when compared to daylight, a blackbody, or anotherlighting reference standard.

The method 1500 and related devices might be useful in the context ofstreet lighting, dashboard lighting, accent lighting, cabin generallighting unit, or headlights, as the (e.g, steady, non-oscillatory)first light having the peak intensity between 400 to 440 nm willgenerally inhibit changes in a subject's circadian rhythm. For example,the first light might have a substantially constant intensity that doesnot vary by more than 5-10% over time.

ADDITIONAL EXAMPLES

The following includes further details related to the methods andsystems described above.

Method for increasing efficacy of intrinsically photosensitive retinalganglion cell activity in humans by targeting upstream retinal circuitry

Within examples, a light source temporospectrally modulates such toexcite intrinsically photosensitive retinal ganglion cells (ipRGCs) inthe eye which project to circadian rhythm centers in the brain. Specificwavelengths and temporal sequences of lights are presented to drivespectrally opponent inputs from signals originating in the conephotoreceptors to ipRGCs which project to brain centers involved innon-image forming vision and mediate functions related to circadianrhythms, arousal and sleep. Light stimuli described in this disclosureare presented by themselves or superimposed over ambient light to withthe aim of affecting the circadian pathway. The aim of some of themethods disclosed herein is to synchronize, advance, and/or delay theinternal phase of a human circadian activity rhythm and modulate arousaland sleep with the use of low light intensities and particularwavelengths.

The aim of the disclosed methods is to cause delays or advances incircadian rhythm to help an individual synchronize circadian rhythmicityby resetting circadian phase. This may enable better preparation fortime zone shifts to alleviate jet lag, preparation for non-traditionalwork shifts or sudden changes in work habit, staying alert for drivinglate into the evening, delivering therapy for seasonal affect disorder,better maintaining normal regular sleep-wake cycles in adults, children,and infants, better timing of peak mental, emotional, and physicalperformance, and other similar benefits. Previous methods use bright(e.g., 10,000 lux) steady state white, or bright blue (e.g. dominantwavelength ˜480 nm lights), bright steady-state lights containing RGBprimary LEDs that can be controlled individually to match naturalscenes, or steady-state LED lights that contain specific wavelengths.Previous references purport to explain the direct effect of changingmelatonin levels on circadian rhythm. While exciting the circadianpathway via modulation of upstream cones or ipRGCs does suppress theproduction of melatonin in the body, melatonin is merely a marker ofcircadian phase, and there is no evidence that it can influence thecircadian rhythm. Therefore, indirect suppression of melatoninproduction is possible, but there is no evidence to support claims thatmelatonin affects the circadian rhythm.

Examples include a spectorotemporal light source designed to stimulateipRGCs by capitalizing on their spectrally opponent response properties.Inputs from long wavelength sensitive (L-) and middle wavelengthsensitive (M-) cones excite ipRGCs, and inputs from short wavelengthsensitive (S-) cone photoreceptors inhibit them. IpRGCs are extremelysensitive to lights in the 500 nm-630 nm wavelength range that areabsorbed by the L/M cones. However, their responses to steady L/M conestimulation are transient such that driving cone based responses inipRGCs with a temporally modulated spectrally opponent stimulus thatalternately stimulates S cones and L/M cones may be useful. Lights thatstimulate S-cones drive responses in ipRGCs at their offset and lightsthat stimulate L/M cones drive ipRGCs at their onset. Thus, stimuli thatcombine offset of S-cone stimuli followed by the onset of L/M conestimuli are capable of driving ipRGCs with low light intensities. Alight producing alternating S-cone and L/M cone stimulation can producestrong continuous activity in the ipRGCs.

The ipRGC, in turn, send their axons to the suprachiasmatic nuclei(SCN), the circadian master clock in the brain, the pregeniculatenucleus (PGN) and other centers involved in arousal and sleep. Sincecone driven responses have different temporal characteristics, spectraltuning and sensitivity than responses that are driven by the intrinsicphotosensitivity of the ipRGCs, the disclosed methods use specificwavelengths (or wavebands) and temporal sequences to drive ipRGCresponses at light levels as much as 1,000 times lower than thoserequired to drive them by stimulating their intrinsic photo-response.Because the upstream cone photoreceptors effectively respond to lowerlight intensities via gain mechanisms, the stimulated ipRGCs send robustsignals to the brain capable of synchronizing circadian rhythm withinthe human body.

Examples include the subsequent applications such as a luminaire,personal lighting device, or transportation cabin light.

Circadian rhythm is reference to an internal clock that governs sleepand awake cycles, whereas circadian rhythmicity includes sleep, physicalactivity, alertness, hormone levels, body temperature, immune function,and digestive activity. Circadian rhythm is controlled by thesuprachiasmatic nucleus (SCN), which serves as the body's “masterclock.” The SCN synchronizes rhythms across the entire body, andcircadian rhythmicity is lost if SCN function is disrupted or destroyed.The SCN maintains control across the body by synchronizing slaveoscillators, which exhibit their own near-24-hour rhythms andsubsequently control circadian phenomena in local tissue.Synchronization of this internal clock to the external Earth-based24-hour cycle will be referred to herein as circadian entrainment.

Given the SCN in the hypothalamus acts as the master clock for circadianrhythmicity, it follows that cells connecting upstream of the SCN willbe involved in circadian entrainment. Experiments have been done using amodified retrograde rabies virus. Rabies viruses have the uniqueproperty that they jump synapses backwards, following inputs backwardstoward the origin. When this virus was injected into the SCN, itfollowed most inputs back to the retina, implicating light as thefeature of the natural world that governs our sleep/wake cycles. Theneural pathway from the retina to the SCN is known as theretinohypothalalmic tract.

The specific retinal cells identified in the retina are a subtype ofganglion cell called the intrinsically photosensitive retinal ganglioncells (ipRGC). IpRGCs are relatively large cells that distribute theirdendrites coarsely, creating a sparse, but complete, mosaic across theretina. The unique feature of these cells is that they are“intrinsically photosensitive.” This is because they express a lightsensitive protein called melanopsin, which is in the same class ofprotein as those found in rod and cone photoreceptors. The presence ofmelanopsin means that the ipRGC can respond to light directly withoutinputs from other neurons.

The discovery of a ganglion cell expressing a light sensitive moleculeintrinsically, was surprising. This is because axons of the ganglioncells form the optic nerve of the eye serving the function oftransmitting signal from the eye to the brain. Conventionally, ganglioncells were known to transmit signals from the photoreceptor cells of theeye (rods and cones) which function to transduce light energy intoneural signals but not be light sensitive themselves.

To date, products involved in producing signals down theretinohypothalalmic pathway have focused on stimulating melanopsininside the ipRGC. Melanopsin peaks at 480 nm, which is perceptually bluelight. It also is sparsely distributed throughout the dendrites,requiring large amounts of light to directly activate the cell. However,despite the presence of melanopsin, ipRGCs do have inputs from othercell types. There are light sensitive cells upstream of the ganglioncells called rod and cone photoreceptors. Cone and rod photoreceptorstile the back of the eye creating a high-density mosaic sufficient tomediate human vision, and both cones and rods exist in a geometricorientation where the long, cylindrical portion that is filled withlight sensitive protein, is parallel to light entering the eye,increasing the probability of an interaction between light and themolecule. Being highly specialized for absorbing light rod and conephotoreceptor activation of ipRGCs occurs at light levels about 1,000lower than lights that stimulate ipRGCs directly. Rod photoreceptorsserve vision under dim light as occurs at night while cones areresponsible for daytime vision.

Cones are of three types long-wavelength-sensitive (L), middlewavelength-sensitive (M), and short wavelength-sensitive (S). The wordslong, middle, and short refer to the part of the electromagneticspectrum to which the molecule is tuned, giving rise to the commonlyrecognized terms used to describe them; red, green, and blue cones,respectively.

Cones and rods are both upstream of the ipRGC. When they are activated,the retinal wiring upstream leads to either excitation or inhibitiononto the ipRGC. The S-cone input to ipRGCs is inhibitory. Thus, ipRGCsare inhibited by the onset of S-cone stimulating lights and they areexcited by their offset. When M- and L-cones are activated, they excitethe ipRGC sending action potentials to the SCN (FIG. 5). Rods also feedinto the ipRGC in an excitatory way.

The spectral tuning of melanopsin is 480 nm, L-opsin peaks between 555and 559 nm in color-normal humans, M-opsin peaks at 530 nm, and S opsinpeaks at 419 nm. FIG. 6 illustrates the relative photopigment curves inhumans, showing where each receptor is responsive to photons within eachwaveband.

Melanopsin inside the ipRGC and the L+M cones activate the ipRGCs withthe relative amount of light required being designated by thephotopigment curves. Light stimuli that activate S-cones inhibit theipRGC activity, and the offset of S-cone activation releases inhibitionon the ipRGC causes action potentials in the ipRGC.

FIG. 4 illustrates the activity of ipRGCs from the L and M cones whenfirst triggered by the peak respective wavelengths. As shown, ipRGCsproduce transient responses to cone stimuli, being most activeimmediately after light onset, but with the activity slowing even thoughthe light stimulation continues. Alternatively, the ipRGCs are inhibitedwhen the S cones stimulated; but when the S cones are not activated theipRGCs can be activated but lights that stimulate L and M cones andmelanopsin as shown in FIG. 3.

Previously in designing lights capable of manipulating human circadianrhythms, mood, alertness and sleep it has been assumed that melanopsin,the nonvisual opsin present in ipRGCs is the main photopigment involvedin circadian photoentrainment in vertebrates, suggesting thatcontributions from other pigments can be ignored. This is true underlaboratory conditions in which these ideas have been tested. Melanopsinis best stimulated by steady, diffuse, bright light. However, becauseipRGC responses to rod and cone contributions are transient and rodinputs saturate at high light levels, bright diffuse steady lights arepoor stimuli for rod and cone inputs to the circadian system. However,the situation is reversed in the natural world where there are frequenttransitions between light and shadow and where the light bombarding theeye constantly changes color as an animal darts through its environment.The response thresholds of the ipRGCs are orders of magnitude lower forbrief increments of colored light incident on the cones than for thesame lights acting on the intrinsic photopigment; thus, under manynatural conditions, the melanopsin contribution becomes negligible.Thus, modulating the temporal and chromatic properties of the lightoutput as disclosed herein provides a much more natural and effectivestimulus for manipulating circadian phase and influencing activityrhythms, mood, arousal and sleep.

Besides its role in circadian behavior, the non-image forming visualsystem that receives input from ipRGCs also is responsible for thepupillary light response. Bright lights cause to pupil to constrictsaving the eye from light damage. It is beneficial that the pupil remainconstricted as long as damaging light levels are present. The pupillarylight response cannot be driven by rods and cones because ipRGCs onlyrespond transiently to their stimulation. Thus, in natural world theintrinsic photopigment in ipRGCs serves as a protective mechanismkeeping the pupils constricted under very high light levels. However,under natural conditions stimulation of the rods and cones is the mostimportant mediator of circadian photoentrainment.

Cone photoreceptors originally evolved to provide animals withinformation about circadian time in the natural world, and that thissystem continues to serve this function in humans. The sustainedresponse characteristics produced by melanopsin are ideally suited todrive the pupillary light reflex, suggesting that it evolved for thatpurpose. The fact that melanopsin can provide significant input to thecircadian system under conditions where rods and cones are disabled,such as in animals with photoreceptor degeneration or in the case ofexposure to bright, steady, uniform laboratory lighting is apparently avestige of the suprachiasmatic nucleus (SCN) and olivary pretectalnucleus (OPN) both using information from the retina that is multiplexedon the same ganglion cell conduit.

While it is true that previous methods designed to stimulate ipRGCs bydriving melanopsin are effective when they produce painfully high lightlevels of >5,000 lux, a much more natural and efficient method toaccomplish the same end is described here.

Disclosed methods involve a light source that targets color opponentinputs to ipRGCs from the L-, M- and S-cone photoreceptors and modulatesthem chromato-temporally to drive the circadian rhythm entrainmentpathway. Knowing that the ganglion cell responsible for synapsing intothe circadian rhythm centers in the brain has converging L- and M-coneexcitatory inputs and inhibitory S-cone input, the light source producesL+M and S stimulation 180 degrees out of phase from one another. L- andM-cones feed this system in the same sign, therefore combined they havea maximum sensitivity of about 550 nm, but with sufficient sensitivityto drive them between about 500 and 630 nm. S-cones are maximallysensitive to 419 nm, but lights between 400 and 480 nm can producestrong S-cone responses. Examples involve producing a light that will beuseful to produce activity in the ipRGCs (circadian pathway) tosynchronize the SCN master clock and stimulate other centers involved incircadian rhythm, mood, activity, arousal and sleep. Thechromato-temporal nature of the light exploits that fact that the highfiring rate the ipRGCs result from the upstream L+M vs S cone signaling.The short wavelength stimulus suppresses activity in the ipRGC thereforepriming it. When the L+M stimulus is exchanged for the S, immediate andfast firing trains of action potentials are sent down the axon to theSCN. Alternation of L/M and S stimuli results in strong continuousactivation of the ipRGCs.

Temporally, various waveforms that can be used for generating the L+Mand the S stimuli which will ultimately excite the ipRGC. Square, sine,and ramp waves will work, as well as other timings that modulate betweenthe L+M and S chromatic stimuli may achieve desired results. Cones areunable to respond to very high temporal frequencies. Also, bursts ofmaximal firing rate in the ipRGCs are only sustained for shortdurations, making low frequency stimulation suboptimal. Therefore,target modulation frequencies to achieve maximum signaling down theipRGC pathway is between 0.1 and 100 Hz. Duty cycles between L+M and Sstimulation are implemented at 50%, although L+M 1%<duty cycles<99% willproduce significant responses.

The light sensitive molecule intrinsic to the ipRGCs (melanopsinganglion cell) has a peak sensitivity of 480 nm. Stimulation by lightcentering at 480 nm +/−20 nm can directly stimulate the pathway, but toactivate the intrinsic photopigment molecule light intensities should beat least 5000 lux. Previous methods for driving the retinohypothalamicpathway have attempted to directly stimulate the intrinsic melanopsinmolecule (e.g. blue light Seasonal Affective Disorder (SAD) lights). Thereason why higher intensity light is required is because of the lowmolecular density of melanopsin inside the ganglion cell, ipRGCs make upless than 0.2% of all cells that are light sensitive, and because theorientation and shape of the ipRGC creates a low surface area wherelight can interact with the molecule. Previously, intensities ofdiffuse, steady blue lights less than 5000 lux and broadband “white”light less than 10,000 lux have been shown to be insufficient tostimulate the retinohypothalamic pathway. In contrast, the conephotoreceptors upstream of the ipRGC can operate at less than 1 lux.Thus, significantly lower light levels can be used for more comfortableuser experience and small, portable products with long battery lives tobe produced that are as effective as large desk lights that produce10,000 lux.

FIG. 7 shows a phase response curve. Relative to an individual'sendogenous circadian phase, light pulses from the light source describedin this disclosure given at different times of day may either (1) donothing, (2) phase delay, or (3) phase advance an individual. The dottedline in FIG. 8 graphically represents circadian rhythm phase advance. Toadvance the circadian rhythm, L+M vs S cone driven responses through theipRGC should occur in the area above the horizontal axis in FIG. 7. FIG.9 graphically represents circadian rhythm phase delay. To delay thecircadian rhythm, L+M vs S cone signal through the ipRGC should occurbelow the horizontal axis of FIG. 7. (Czeisler) Reference: “A phaseresponse curve to single bright light pulses in human subjects”, Sat BirS. Khalsa, Megan E. Jewett, Christian Cajochen and Charles A. Czeisler.

FIG. 10 represents a spectral power curve for a commercially viableconstant or steady state light source that would be useful fortraditional work shifts, where humans are on a similar circadian rhythm,to create a phase advance in circadian rhythm to peak earlier in theday, and a phase delay for synchronization in the afternoon. This typeof advance-delay cycle simulates the natural accordion effect ofsunlight to set, reset, and synchronize circadian rhythm in humans; butwith higher efficacy as the focus is on the L+M cone photoreceptors byusing a higher percentage of total luminous flux in the 500-630 nmwavelength range. This is not as productive for high phase shift ratesas the alternated peak wavelength light sources, but will trigger steadyganglion cell response and influence the circadian phase.

For example, an 800-lumen light source, with the higher percentage of500-630 nm light will excite more ipRGC activity due to the higherprobability of photons targeting L+M cone photoreceptors; as opposed toan 800 lumen light source with a higher percentage of light in the peakblue (480 nm) wavelength range to target melanopsin ganglion cells.Because interior lighting doesn't have illuminance values as high assunlight, directly replicating the full spectral curve of sunlight willbe less efficacious as sunlight during day peaks between 440-500 nm.

Other recent research, however, has demonstrated that the contributionof melanopsin alone may not be responsible for synchronizing circadianactivity outside of the artificial photoperiods used in the laboratory.Mice lacking rods fail to entrain to experimental photoperiods withillumination of less than 1 lux (Ebihara and Tsuji, 1980 and Mrosovsky,2003). Furthermore, mice lacking a middle-wavelength-sensitive cone, butwith intact melanopsin ganglion cells, could not entrain to standardlaboratory photoperiods of 10 lux or to a 15 min pulse of 530 nm light,but could entrain to 15 min pulses of 360 nm and 480 nm light(Dkhissi-Benyahya et al. 2007). Thus, a circadian system reliant uponmelanopsin alone would be insensitive to the longer wavelengths of lightprevalent at dawn and dusk, and this effect was recapitulated within ourexperiments.

The previous example refers to the probability of hitting L+M conephotoreceptors with photons being orders of magnitude higher than theprobability of photons hitting melanopsin ganglion cells; thus with thetotal number of photons available being equal in each range, comparingtwo different sources, a light source peaking in the L+M opsin rangewill trigger more ganglion cell activity.

EXAMPLE EMBODIMENTS

A modulating light source using LED(s), but not limited to, consistingof violet light peaking at a wavelength between 400-480 nm and a minimumpeak illuminance of 0.1 lux at the eye, and a light peaking at awavelength between 500-630 nm and a minimum peak illuminance of 0.1 luxat the eye; opposing modulation consisting of, but not limited tosquare, sine, or triangular waves of less than 100 Hz for the purpose ofcausing an advance or delay in circadian rhythm; use as a therapy lightfor seasonal affect disorder; and/or use as a mood enhancer.

A modulating light source using LED(s), but not limited to, consistingof violet light peaking at a wavelength between 400-480 nm and a minimumpeak illuminance of 0.1 lux at the eye with the presence of ambientlight, whereas the modulation consists of, but not limited to square,sine, or triangular waves of less than 100 Hz for the purpose of causingan advance or delay in circadian rhythm; use as a therapy light forseasonal affect disorder; and/or use as a mood enhancer.

A steady light source using LED(s), but not limited to, fixed at 0 Hz ormodulating at frequencies greater than 0.1 Hz, consisting of lightsources with peak wavelength between 470-580 nm, with the addition oflower percentage luminance of high CRI white light sources for thepurpose to focus on L and M-opsin production for photoentrainment incommercial settings as use for a circadian synchronizer, therapy forseasonal affect disorder, and use as mood enhancement for increasedproductivity.

A steady light source using LED(s), but not limited to, fixed at 0 Hz ormodulating greater than 0.1 Hz, consisting of peak wavelength between600-700 nm with the addition of lower spectral power white light sourcewith a high CRI to chromatically shift the white light source for thepurpose of illumination as a circadian non-disruptor.

A high CRI LED that uses phosphors to create a chromatically shifted LEDwith a peak wavelength between 470-580 nm, or a mix of LEDs within alamp to achieve the same high CRI light with peak wavelength between470-580 nm, for the purpose to focus on L and M-opsin production forphotoentrainment in commercial settings as use for a circadiansynchronizer, therapy for seasonal affect disorder, and use as moodenhancement for increased productivity.

A luminaire with architectural, task, area, and reading lightingapplications that use light sources in any of the previous examples.

Personal wearable device applications such as goggles, headbands, armand wrist-wear that use light sources in any of the previous examples.

Automotive and aerospace dash, accent, and cabin general illuminationapplications, and automotive headlights that use light sources in any ofthe previous examples.

Portable illuminating devices that use light sources in any of theprevious examples.

Medical therapy or ambient devices that use light sources in any of theprevious examples.

Backlighting for displays such as cell phones, tablets, computermonitors, televisions, and related that use light sources in any of theprevious examples.

A luminaire or lamp used for infants and children that use light sourcesin any of the previous examples.

A wearable device that is used for shining light onto the retina whilesubjects are asleep that use light sources in any of the previousexamples.

An example is a low intensity flickering light source, with a minimumilluminance of 0.1 lux at the eye, that uses the combination of a shortand long wavelength light sources to shift or synchronize circadianrhythm of humans by triggering intrinsically photosensitive retinalganglion cells. The example is also a higher CRI commercial readysteady-state light source that focuses more on L+M cones RGCsstimulation to shift or synchronize circadian rhythms naturally. Theexample includes the applications that use the flickering light sourcein architectural, portable, personal, automotive, and medical devices toshift circadian rhythm in humans.

An example includes a high CRI “white” LED with peak wavelength between480-580 nm with the presence of light in the visible spectrum from400-780 nm.

An example includes a lamp that uses a combination of the pluralitydiscrete LEDs with a peak between 480-560 nm mixed with high CRI “white”LED's to create a light output that has a peak wavelength between480-580 nm with the presence of light in the visible spectrum from400-780 nm.

An example includes modulating light within the L+M opsinphotosensitivity range along with violet light in the S photosensitivityrange to generate a high level of ganglion cell activity by firing, thenimmediately inhibiting activity in ganglion cells. This is due to L+Mganglion cells being most active immediately after being triggered, thenshut off so they can be fired again; along with S ganglion cells beingactive immediately after elimination of violet light. Compared to bluelight, this is a higher efficacy use of photons to influence circadianphase.

This can be done with modulating blue (melanopsin) and violet light aswell; but since half the photons of blue light actually make it throughthe lens, and melanopsin ganglion cells are far fewer and smaller thanL+M cones, the probability of photons targeting melanopsin ganglioncells is much lower than photons targeting L+M ganglion cells.

Targeting L+M ganglion cells is more efficacious than targetingMelanopsin ganglion cells with both modulating and steady light.

Melatonin is not a circadian phase driver; Melatonin is a hormone and isonly an indicator of circadian phase, it is lowest when a person is atpeak phase (˜noon), and highest when person is at base phase(˜midnight).

Measuring melatonin levels in humans is used as circadian phaseindication due to the ease of melatonin measurement in saliva and blood.Other hormones can be used as circadian phase indicators as they peakand valley during specific points of circadian phase, but aren't aseasily measured for correlation. Many people confuse melanopsin andmelatonin as being related, but there is no correlation.

Visible wavelengths of light do not suppress or generate melatoninsecretion. The body produces the hormone melatonin at varying levelsthroughout the day as a result of phase synchronization in the humanbody regardless of presence of visible light.

All hormones in the human body will synchronize accordingly to circadianphase. Proteins (opsins), not hormones (such as melatonin), are what isgenerated and inhibited in the retina by visible light.

Circadian phase advances and delays can't be driven by visible light atanytime during the day. Circadian phase advance (peaking earlier) onlyoccurs before the individual peaks; and circadian phase delays (dippinglater) only occurs after the individual peaks.

As used herein, the term “correlated color temperature (CCT)” may referto the apparent color of light emitted from the characterized lightsource as compared to the color of light emitted by iron at eachrespective temperature in degrees Kelvin.

While various example aspects and example embodiments have beendisclosed herein, other aspects and embodiments will be apparent tothose skilled in the art. The various example aspects and exampleembodiments disclosed herein are for purposes of illustration and arenot intended to be limiting, with the true scope and spirit beingindicated by the following claims.

What is claimed is:
 1. A device comprising: a light source assembly; anda control system configured to cause the light source assembly toperform functions comprising: emitting a first light having a firstluminous flux and a peak intensity at a first wavelength that is greaterthan or equal to 680 nanometers (nm) and less than or equal to 750 nm,wherein the first luminous flux is variable or the emission of the firstlight is interrupted one or more times; and emitting a second lighthaving a second luminous flux and a peak intensity at a secondwavelength that is less than or equal to 680 nm, wherein the secondluminous flux is variable or the emission of the second light isinterrupted one or more times, wherein the first luminous flux is at amaximum at least during a time at which the second luminous flux is notat a maximum.
 2. The device of claim 1, wherein the light sourceassembly comprises a first light source configured to emit the firstlight and a second light source configured to emit the second light. 3.The device of claim 1, wherein the first luminous flux is out of phasewith the second luminous flux.
 4. The device of claim 1, wherein thefirst luminous flux takes the form of a square wave, a sinusoidal wave,a sawtooth wave, or a triangle wave.
 5. The device of claim 1, whereinthe second luminous flux takes the form of a square wave, a sinusoidalwave, a sawtooth wave, or a triangle wave.
 6. The device of claim 1,wherein the first luminous flux and the second luminous flux take theform of waveforms having equal respective duty cycles.
 7. The device ofclaim 1, wherein the first luminous flux and the second luminous fluxtake the form of waveforms having unequal respective duty cycles.
 8. Thedevice of claim 1, wherein at least 50%, at least 60%, at least 70%, atleast 80%, at least 90% or at least 95% of a power spectral density ofthe second light corresponds to wavelengths within a range of 440 nm to520 nm.
 9. The device of claim 1, wherein at least 50%, at least 60%, atleast 70%, at least 80%, at least 90% or at least 95% of a powerspectral density of the second light corresponds to wavelengths within arange of 520 nm to 600 nm.
 10. A device comprising: a light sourceassembly; and a control system configured to cause the light sourceassembly to perform functions comprising: emitting a first light havinga first luminous flux and a peak intensity at a first wavelength that isgreater than or equal to 400 nanometers (nm) and less than or equal to440 nm, wherein the first luminous flux is variable or the emission ofthe first light is interrupted one or more times; and emitting a secondlight having a second luminous flux and a peak intensity at a secondwavelength that is greater than or equal to 440 nm, wherein the secondluminous flux is variable or the emission of the second light isinterrupted one or more times, wherein the first luminous flux is at amaximum at least during a time at which the second luminous flux is notat a maximum.
 11. The device of claim 10, wherein the light sourceassembly comprises a first light source configured to emit the firstlight and a second light source configured to emit the second light. 12.The device of claim 10, wherein the first luminous flux is out of phasewith the second luminous flux.
 13. The device of claim 10, wherein thefirst luminous flux takes the form of a square wave, a sinusoidal wave,a sawtooth wave, or a triangle wave.
 14. The device of claim 10, whereinthe second luminous flux takes the form of a square wave, a sinusoidalwave, a sawtooth wave, or a triangle wave.
 15. The device of claim 10,wherein the first luminous flux and the second luminous flux take theform of waveforms having equal respective duty cycles.
 16. The device ofclaim 10, wherein the first luminous flux and the second luminous fluxtake the form of waveforms having unequal respective duty cycles. 17.The device of claim 10, wherein at least 50%, at least 60%, at least70%, at least 80%, at least 90% or at least 95% of a power spectraldensity of the first light corresponds to wavelengths within a range of400 nm to 415 nm.
 18. The device of claim 10, wherein at least 50%, atleast 60%, at least 70%, at least 80%, at least 90% or at least 95% of apower spectral density of the first light corresponds to wavelengthswithin a range of 415 nm to 430 nm.
 19. A light source comprising: oneor more first light emitting diodes (LEDs) configured to emit firstlight having a peak intensity within a range of 400 nm to 440 nm; andone or more second LEDs configured to emit second light having a peakintensity greater than 440 nm, the first light and the second lightcombined having a peak intensity at a wavelength within a range of 400nm to 440 nm.
 20. The light source of claim 19, wherein the second lighthas a color rendering index higher than 70 when compared to daylight, ablackbody, or another lighting reference standard.